The management of sub-contractors and material suppliers is vital for building construction management which requires a great deal of workers or materials. However, it is difficult to find an appropriate data source for investigating this management information itself, particularly time sequential data. The Shimizu Corporation (“Shimizu-Gumi” in the post-war era) has stored approximately 3,000 construction reports from the post-war era (1923–1941), in which the types of businesses of the sub-contractors or material suppliers is recorded, such as carpentry, plastering, and supply of lumber or cements, among others. The aim of this paper is to investigate the actual condition and the changes introduced in the process of the management of sub-contractors and material suppliers by Shimizu-Gumi in the post-war era. Shimizu-Gumi has been one of the largest general contractors in Japan since the 18th century.
The authors recorded the types of businesses of house construction (510 records) and office construction (360 records). Up to 30–36 types of businesses are recorded in each construction report. The authors calculated the “appearance rate” and the “average number of businesses.” The “appearance rate” is the percentage of the construction reports which recorded the name of the target type of business in the total construction reports. The “average number of businesses” is, on an average, how many times the type of business is recorded in one construction report. In some cases, a type of business is recorded more than once in one construction report.
The findings are as follows:
1. In house construction, there are 47 types of businesses where the appearance rate is more than 5%, while there are 52 types in office construction, among which 43 types are common. The types of businesses in which the appearance rate is high are carpentry, plastering, and scaffolding, among others. The type of business in which the appearance rate is low is mainly supply of materials, which deals with finishing materials.
2. In office construction, the comparison between wooden construction and non-wooden construction (reinforced concrete, steel, etc.) revealed the difference in the appearance rate or changing process, such as the appearance rate of tiles increasing first in wooden office construction and then in non-wooden construction.
3. The appearance rate increased or decreased in several types of businesses. Some of these changes corresponded to previous studies, such as the increase of “tobi-doko” (the integration of tobi, scaffolders, and doko, earth workers) or the increase of tiles and decrease of bricks.
4. There are approximately five types of businesses in which the average number of businesses is more than 1. In the business of metal doors, according to one construction report, data regarding workers (sub-contractors for construction) and material suppliers are recorded.
In future studies, the authors will investigate the names of the workers or companies recorded in the construction reports. This will elucidate the selection of workers or material suppliers by the general contractor, the difference between workers of material suppliers in house construction and office construction, and the changing process of types of businesses by the same workers or material suppliers. In addition, further analysis is required to establish whether these findings can be applied to other general contractors or other types of constructions.
